The ever increasing availability and popularity of wireless communication can be linked to technological gains that have provided more efficient, reliable and cost-effective mobile devices, such as message pagers, wireless telephones and personal communication services ("PCS") devices, as examples. Due to their mobility and low power requirements, conventional mobile devices impose significant design constraints upon the wireless communication networks and base stations that support them. Nevertheless, the demand for better and cheaper mobile devices and wireless communication services continues to grow at a rapid pace.
The selection of one mobile device over another is usually the result of a simple cost benefit analysis--the cost of a particular mobile device, the anticipated life span for that device, the usefulness of the various services that can be subscribed to using the device, etc. Message paging subscribers, for instance, demand powerful and sophisticated features (e.g., voice mail, e-mail, wide area paging, out of area roaming, voice messaging, voice response, etc.) that often conflict with the physical restrictions of minimized size and increased battery life--the size of conventional pagers makes it difficult to incorporate advanced features requiring interaction with the subscriber (e.g., integration of control switches/keypads into message pager).
The trend to enhance services has been to incorporate automated call processing techniques into communication systems and system services. Many contemporary message paging systems, for instance, include automated interfaces for interacting with callers. Commonly, these systems enable a caller to the system to leave a message for a subscriber of the system by leaving a call-back number using the telephone keypad.
More advanced systems enable callers to interact with the system by responding to system queries using their telephone keypads. At some point during this interaction, the caller is asked whether he wishes to leave a "text" (alphanumeric) or voice (e.g., voice mail, voice message page, etc.) message. A positive response concerning the "text" message will cause the system to transfer the caller to a system operator to whom the caller dictates a message. After the dictation is complete, the system operator often verifies the text message by reading the same back to the caller. Following the caller's approval, the text message is then transmitted to the subscriber.
There is desire and need in the art to increase the utility of such call processing systems by having them recognize speech. A suitable speech recognition system will automate, at least in part, the foregoing dictation process, that not only will translate voice to text for delivery of voice messages to text pagers, but allow file based automated processing of messages.
Speech recognition, by definition, is the ability of a system to understand human speech. A speech recognition system usually is made up of an input device, a voice board that provides analog-to-digital conversion of a speech signal, and a signal processing module that uses patterns to recognize the speech signal. To be acceptable, the speech recognition system must rapidly and accurately recognize a wide range of words and phrases (a vocabulary), such as the thousands words and phrase used by callers into message paging systems. In current speech recognition systems, as the vocabulary that can be recognized increases, the speed and accuracy are reduced, as the speech recognition system must search through more possibilities, and the number of similar-sounding words and phrases increases. These problems have limited the practical uses of speech recognition systems.